Headlight-On Warning Beeper for a 1986 Honda CRX Si

The idea of adding a warning beeper when you leave the headlights on in your CRX came from Todd Kneib's Del Sol page. Adding this to a CRX is not as simple as on a Del Sol, but very similar. The main idea is to simulate leaving the key in the ignition switch when the parking lights are on. Adding a single 12vdc SPST relay will do this, all for about $10. The key-in beeper will now sound if:

(1) the parking or headlights are on AND

(2) you unbuckle the driver's seat belt AND

(3) You open either door.

Items needed: Radio Shack Automotive relay (#275-226) for $5.99; 4 pieces of ~20 ga. wire 18" long; 4 wire tap-ins (RS #64-3053 includes 7 for $1.69); 4 each 18-22 ga.1/4" female quick disconnects (Checker Auto had 21 for $1.69). The relay is rated at 30A and is really overkill. However, it only draws 200 ma at 13.2vdc and should not cause the parking light switch/wiring much added load.. Any 12vdc relay will do.

Tools needed: a voltmeter, Phillips screwdrivers, wire cutter, wire stripper, crimping tool, electrical tape and double stick foam tape to keep relay from bouncing around.

Circuit Description: A relay is a switch that turns on (closes) when 12 volts is applied to the coil. The RS relay actually turns on when > 6 volts are applied, and turns off when < 3.6 volts are applied. The schematic at the right shows the relay and the pin outs as viewed from the bottom of the relay (blades pointing upwards). We connect the switch in parallel to the ignition "Key-in" switch, pin 30/51 to one and pin 87 to the other. We connect the coil 12vdc (+) pin 86 to the parking light power and the coil ground (-) pin 85 to the door open switch ground.

Connection #1: On my 86 CRX Si, the 2 key-in sensing switch wires came out of the steering column wire-set in a separate 2 circuit snap connector. One wire is White/Blue (the hot side of the switch) and the other is Blue/White. Tap into both of these wires on the side away from the steering wheel (toward the fuse box) and connect these tap wires to 30/51 and 87 on the relay. It does not matter which goes where.

Connection #2: Rather than taking apart the steering wheel to trace the parking light wire, I found it at the connector for the Side Marker Control module. Its location and schematic are at the right. The wire we want is colored Red/Black with 2 blue spots on it. The side marker control is way up under the dash, behind the fuse box, against the left wheel well. It has 7 wires in an 8-circuit connector plugged into it. To check you have the right wire, disconnect the 8-circuit connector and check the R/Bl wire for 12VDC when light switch is on, 0VDC when it is off. Tap into this wire, not necessarily adjacent to the Side Marker Control module, and connect to 86 on the relay. This R/Bl (red with black stripe) wire can probably also be found in the connector of the instrument panel dimmer control.

Connection #3: Now the tricky part. We need to ground the relay coil in a special way. We must find the ground that is used to light the interior light. This ground is supposedly green with red stripe (G/R). Unscrew the driver side door switch (I am sure the door is already open) and remove it and note the color of the wire G/R. Ground this wire by opening the door and the interior light goes on. Close the door, the ground is lost, and the light goes out. In the schematic below, the G/R wire goes to both door switches and to the Seat Belt Beeper/Timer Unit. The diagram on the left is the schematic and the location diagram is on the right. Remove the dash lower panel to find the beeper unit. It has a 6-connector plug. One of the key-in switch wires goes there (Bu/W wire). My connector may have been rewired, because the ground wire was not G/R, as in the schematic, but rather Blue/Red (Bu/R). It was positioned as the middle contact on the row opposite the retaining clip. The only way to be certain is to check for continuity (0 ohms) from that contact to the wire in the door switch (which is still removed, right?) Be careful, as there is 12VDC on many of these contacts and may blow your meter.

When you have found the wire, remove the wrap back along this connector to bare the Bu/R (or whatever color) wire, tap into it and connect to relay 85. Replace the door switch. Reconnect the Seat Belt Beeper/Timer Unit connector and test.

Test: With the door closed and the key out, turn on the parking lights and you should be able to hear the relay click on. If not, test for 12vdc between 86 and 85. Turn off lights and hear relay click off. Turn lights back on, open the door. The interior light should turn on and the beeper, too. Now turn off lights and beeper should be silent. Be sure the driver side seat belt is not engaged: the beeper is disabled for both the key-in and the lights-on function whenever the seat belt is engaged. Cool.

Finish: Once it all works, you may want to tape up the 4 wires into a neat bundle, and then, with a one inch square piece of double stick tape, attach a flat side of the relay to the painted metal up above the steering column clear out of the way. Others may want to screw it somewhere underneath, but tape was fine for me. Replace the dash lower panel. No more dead batteries (from THAT, at least).

Please let me know it there are mistakes or additional info on this project. Disclaimer: Perform this at your own risk.